Sensory qualities of plain white pan bread: Influence of farming system, year of harvest and baking technique

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Abstract

The sensory qualities of products from sustainable production systems are not well known, but important for development of such systems. To understand how wheat growing systems and baking processes influence white bread quality, six samples of wheat (Triticum aestivum, var.Ebi) from field trials harvested in two consecutive years, three grown in conventional farming systems and three in organic farming systems (biodynamic and ecological), were milled on the Bühler laboratory mill. Flours were extracted to a fixed ash content (0.48% dmb) and analysed qualitatively and quantitatively. A total of twenty one bread types were baked: twelve according to the farinographic data and nine according to modified recipes. Ten selected and trained assessors completed a sensory analysis (a descriptive profiling test) with three replicates using seventeen sensory attributes.

The slice area was established using image analysis. There were no differences in slice area between bread baked with conventionally or organically grown bread baked with organically grown wheat harvested in 1999, yet there were differences in 2000, such that slice area was larger for the conventional samples. The effect of year was greater than the effect of farming system or recipe modification, and differences in the sensory data was explained more by texture than by aroma and flavour attributes. Breads baked with wheat harvested in 1999 had significantly lower intensity of crumb attributes such as elasticity, smoothness and juiciness, but higher rancid flavour, springiness, compressibility, mastication resistance and lower colour intensity, as well as higher crust toughness, than did breads baked with wheat harvested in 2000. Breads baked with conventional flour had significantly higher elasticity and juiciness than breads baked with organic flour. Several interactions between year and farming system were revealed.

Introduction

Wheat is the most common cereal used for bread production in Sweden. The Swedish government has proclaimed sustainable development as a political vision, with environmentally friendly methods for agricultural production as one focus. To stimulate the development of alternative farming systems, the government has a goal to increase the share of organically cultivated arable land (Jordbruksdepartementet, 1999). It would seem that this can only be achieved and maintained if consumer demand for organically produced food is large enough to give the production system sufficient momentum to enable such a development. The Swedish interdisciplinary research program FOOD21 (2003) has been established to focus on sustainability in agricultural production, product quality and consumer demands. This study is the second part of a larger investigation within the FOOD 21 program. In the first part, the sensory qualities of whole wheat breads baked with three conventional and three organic samples of wheat, defined in accordance with a Council Regulation (EC) (1991) and grown in field trials, were described in relation to milling and baking techniques (Kihlberg et al., 2004). With respect to farming system the results showed that the breads baked with two of three organic wheat samples were most influenced by bran characteristics, while the third organic wheat sample had a sensory profile dominated by endosperm character and was similar to the sensory profile of breads baked with conventional wheat. In the present study, the effects of bran have been eliminated to expose other less dominating effects. An increase in flour extraction rate implies a negative effect on loaf volume (Galliard, 1987, Pomeranz et al., 1977), while a decrease results in lighter colour and reduced nutritional value of the bread (Jones and Ziegler, 1964). In white leavened bread, the gluten matrix is not influenced by bran material, thus the texture and volume of white bread may be related more to the effect of gluten proteins than in whole wheat bread.

The sensory quality of bread is influenced by many factors at each step in the production chain, from wheat cultivation to bread packaging. Growth location influences the rheological properties of dough made with conventional versus organic wheat grown in field trials (Gunnarsson and Haslund, 1995). Factors such as type of soil, climate (Samuel and East, 1990, Zhu and Khan, 2002), time and year of harvest (Andersson, 1994, Andersson et al., 1994, Westerlund et al., 1991) influence the quality of wheat, but also the type of milling and baking technique affect the sensory quality of the bread (Færgestad et al., 1999, Kihlberg et al., 2004). To investigate product quality and to support further development of new alternative production systems, it is necessary to understand the relationships between these individual factors and their effects on end-product (white bread) quality along the production chain. The milling industry has established an index of bread-making potential for wheat at the point of trade, involving parameters such as protein content, FN and volume weight. The protein content is an important measure of flour baking performance, as it is highly correlated with loaf volume (Finney and Barmore, 1948, Preston et al., 1992). Also, protein quality is of importance (Eliasson and Larsson, 1993a) and for flours with relatively low protein content (≤12%), the total amount of gluten proteins was shown to be more important for loaf volume than the amount of a single protein type (Wieser and Kieffer, 2001).

To meet industry demands, wheat breeding programs focus on introducing wheat varieties with higher protein content (Fajersson and Svensson, 1985, Svensson, 1981). Experiments with different fertilizers, intended to increase protein level, have revealed different responses for different wheat cultivars and a positive correlation between bread yield and total nitrogen content (Fredriksson et al., 1997, Fredriksson et al., 1998). Protein content has often been reported to be lower in organically than in conventionally grown wheat (Gunnarsson and Haslund, 1995, Haglund et al., 1998, Slania, 1995). Moreover, the gluten proteins in biodynamically grown wheat had less residual protein (insoluble in acetic acid) than conventionally grown wheat (Salomonsson and Larsson-Raznikiewicz, 1985).

The objective sensory quality of bread is described by its sensory profile (Lawless and Heyman, 1999) constituted by sensory attributes. These tend to be perceived in the following order: appearance, aroma, texture and flavour (Meilgaard et al., 1991). To produce bread that matches consumer expectations, it is necessary to understand the relationship between flour quality and the baked bread characteristics. Among the most important criteria for buying of bread are good taste and freshness. Swedish consumers believe that organic bread is less tasty, less fresh and has a shorter shelf-life than conventional bread (Magnusson et al., 2001). The objective sensory qualities of white breads baked with wheat grown by different farming systems are not well known, but decisive for further development of sustainable production systems. The aim of this study was to investigate the effect of origin of wheat grown conventionally and organically, harvested during two consecutive years at the same growth location, as well as the effect of recipe modification on the sensory qualities of plain white pan bread.

Section snippets

Experimental overview

White pan breads were baked with winter wheat variety Ebi (from field trials, L4-3410) grown conventionally (lots A-B) and organically (lots C-E). Both wheats were harvested in 1999 and 2000 (Table 1). Extracted and analysed white flours (Table 2) were used for baking of a total of twenty-one bread types. To adapt the baking process to the flour characteristics, breads 1–12 were baked in accordance with the results of the Brabender Farinograph analysis of each of these twelve flours. To study

Overall results

Most of the texture attributes showed significant differences between samples. For aroma and flavour, only a few attributes showed significant differences. The effect of year was greater than the effect of farming system or recipe modification.

Principal component analysis (PCA.)

According to the PCA carried out on the breads' seventeen sensory variables, the total variation in the sensory data was explained up to 91% by PC 1 (63%) and PC 2 (28%). The relationship between sensory attributes is shown in the loading plot (Fig. 1a).

Discussion

This experiment was based on the assumption that by standardizing the processing of the wheat the effects of the experimental factors would not be eliminated, that is, white bread contained valid information for interpretation of the experimental data. The sensory profiles in other bread types, such as whole wheat bread or sourdough bread, are dominated by bran (Kihlberg et al., 2004) or by acids (Marklinder, 1996), and the effect of gluten proteins would be confounded by the effect of these

Conclusions

The flour, dough and bread quality data revealed that the differences between experimental samples were more related to year of harvest than to farming system.

Largest slice area was shown in samples from 2000, and within samples from 2000, conventional samples showed the largest slice area. There were no differences in slice area between breads baked with conventional and organic wheat harvested in 1999.

Samples with the highest versus lowest ratio of wet gluten to protein content resulted in

Acknowledgements

The authors are thankful for the fruitful cooperation and kind help received during the project. This study was part of the FOOD 21 programme (Product Quality Unit) supported by MISTRA, the Foundation for Strategic Environmental Research. The Agricultural Society in Kristianstad (Scania, Sweden) contributed the wheat samples. The Sample Preparation Unit, Swedish Agricultural University, Uppsala, Sweden stored the wheat. Nord Mills AB, Uppsala, Sweden made it possible to conduct the experiment,

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